NASA scientist James Hansen has tracked Earth's temperature for decades, and he is confident the global warming trend of 0.9 degrees Celsius observed since 1880 is mainly the result of human-produced greenhouse gases.
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As Earth's average temperature rises, and most rapidly in the high latitudes, what is happening to the great northern forests of Siberia? Join scientists from NASA and Russia's Academy of Science on an expedition down the Kochechum River in north-central Siberia as they go in search of answers.
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Tropical forests are home to half the Earth's species, and their trees are an immense standing reservoir of carbon. Deforestation will have increasingly serious consequences for biodiversity, humans, and climate.
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A string of dry years shriveled vegetation in Africa's Sahel, causing some to fear that the Sahara Desert was shifting south. Satellite data spanning more than twenty years now shows that the Sahel is holding its own against the Sahara and may be recovering with the return of near-normal rainfall.
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